I “fine tuned” my clamp by filing the bottom ends with a mill bastard file, as mentioned above. This removes the "highs" and brings the middle of the clamp closer to the shaft. Adjusting the off-set through the clamp will bring you closer to perfect as well. Also, as mentioned, run your thumb nail (or other) between the quill and clamp before you apply glue (after with tape) so there is a gap that can compress as you bring the clamp to bare against the shaft. Always check the fletch to shaft contact before allowing to fully dry. Because each quill has a different thickness, you’ll have to tinker with each fletch to get it “just right”. Some fletches will not lend themselves to contacting perfectly. It’s an art.
Good luck!
Kris